A coaxial cable comprising a center conductor covered with a dielectric layer whose outer surface is covered with a shield layer having a conductive wire, and a covering (jacket) covering the outer surface of the shield layer is generally known and is widely used as a high-frequency transmission line. Recently, diameter of the coaxial cable is becoming narrower; for example, a very narrow coaxial cable whose center conductor has a diameter of 0.1 mm or less and whose outer surface has a diameter of about 0.35 mm is being used in electronic devices, such as a compact notebook type personal computer and a cellular phone.
In those electronic devices, for example, a plurality of coaxial cables are used to electrically connect the liquid crystal display section of a notebook type personal computer to the main body portion thereof, and the wiring and connection become complex. As means of easily and surely achieving such complex connection, a flat cable comprising a plurality of coaxial cables held in parallel on the same plane is proposed in JP-A-2004-273333.
At the end portion of the coaxial cable of the conventional flat cable, an outer insulating coat (jacket) and a shield layer are peeled within a range of a first predetermined length from the tip to expose an inner insulating coat (dielectric layer), thereby forming a press fitting portion, and an outer insulating coat (jacket) is peeled, leaving an outer insulating coat (jacket) of a predetermined width on the tip side, within a range of a second predetermined length from an inner end of the press fitting portion, thereby forming a ground connection portion.
According to the flat cable with such a structure, the shield layer exposed at the ground connection portion is held by the outer insulating coat (jacket) of a predetermined width left on the tip side, so that multiple laterally wound narrow electric wires which form the shield layer can be prevented from raveling apart. However, a plurality of coaxial cables are likely to be separated from one another at the end portion of the flat cable, thus making it difficult to accurately hold the pitches formed among the coaxial cables. This brings about a problem of reducing the reliability of connection at the time of making press fitting connection of a connector to the tip of the flat cable and the reliability of connection at the time of connecting the shield layer to the ground. In a case where the tip of the flat cable is connected to press fitting pins of the connector which are arranged at equal intervals, for example, when the individual coaxial cables are separated apart, the work of inserting the coaxial cables into the press fitting pins becomes significantly hard, and the coaxial cables may come off the press fitting pins at the worst, causing a conductive failure.